In a liquid crystal display (LCD) device, a liquid crystal is a substance that does not itself illuminate light. Instead, the liquid crystal relies on receiving light from a light source, thereby displaying images and data. In the case of a typical liquid crystal display device, a backlight module powered by electricity supplies the needed light. Generally, a bottom-lighting type backlight module and/or an edge-lighting type backlight module are/is provided.
Generally, a bottom-lighting type backlight module has two or more light sources, thus making the overall LCD big, heavy, and energy inefficient. Therefore, bottom-lighting type backlight modules are usually employed in LCDs or LCD televisions where portability, mass, and volume are negligible factors.
FIG. 1 represents a typical edge-lighting type backlight module 1. The backlight module 1 includes a light guide plate 11, a light source 12, a reflector 13, and a plurality of optical elements 14, 15, and 16. The light guide device 11 is wedge-shaped. The optical elements include a reflective sheet 14, a diffusion sheet 15, and two prism sheets 16. The light source 12 generally includes a cold cathode fluorescent lamp (CCFL). The reflective sheet 14 is positioned under the light guide plate 11 and is configured for reflecting light back into the light guide plate 11. The diffusion sheet 15 is located above the light guide plate 11 and is configured for uniformly diffusing the emitted light. The prism sheets 16 are positioned above the diffusion sheet 15 and are configured for collimating the emitted light, thereby improving the brightness of light illumination.
Also referring to FIG. 2, two ends of the light source 12, i.e. two electrodes 121 that do not emit light results in that few light enters into two corners of the light guide plate 11 adjacent to the two electrodes 121. Thus, two dark corners 18 are formed. The light source 12 may be configured to extend or displace farther out from the light guide plate 11 to solve the above problem. However, it makes little effect and instead will enlarge the volume of the backlight module 1.
What is needed, therefore, is a light guide device and a backlight module using the same which overcome the above-described problem.